a. Field of the Invention
The current invention relates to extendable masts.
b. Background Art
Many devices are more useful when positioned above ground level. An antenna can transmit and/or receive signals over increased distances by elevating the antenna. Cameras or other surveillance equipment can have a wider field of view and a better vantage point if they are elevated. Lighting can cover a larger area is suspended above ground level. It is desirable for many devices to position the device above ground level. In some cases, the higher the position the better.
One technique used to raise devices is an extendible mast. A device can be mounted to the top of an extendible mast, and then raised above ground level as the mast is extended. This provides an essentially vertical mast extended from a base on the ground. In some instances, the device can be manipulated while extended. For example, a camera can be moved in different directions by rotating the mast or by providing motors with power and controls.
Holding an object at a large distance from a support can be difficult. A long mast can catch the wind, or it can begin to tip in one direction of another. This produces a force that urges the mast to fall over towards the ground. Supporting the base of the mast as a force urges the mast to tip can also cause a mast to bend and even buckle in some cases. A mast serves as a large lever aim, with the fulcrum being the base of the mast as it is supported on the ground. The longer the mast, the more force a given weight at the end of the mast produces to tip and/or bend the mast.
A mast will often be supported by guy lines to counter the effect of the long lever arm. The guy lines provide extra strength and stability. Guy lines will be connected to one or more points along the mast, and these lines will be secured to the ground at a set distance from the base of the mast. Three or more guy lines are usually attached about a single position on a mast, and the opposite ends of the guy lines are secured to the ground at a significant distance from the base of the mast. There can be one or more guy line attachment points along the length of a mast, and the taller the mast the greater the need for guy lines.
Connecting guy lines to a mast can be a time consuming and difficult task. The lines must be connected to the mast, and then taken to a guy line base position removed from the mast base. Often, the guy lines are taken to the guy line base position simultaneously so one line will not serve to pull the mast over as the guy line is extended. This requires several people working in concert to establish a mast with guy lines. It also requires a large footprint, because there are generally at least three guy line base positions extending symmetrically away from the mast base for a considerable distance.
There are many times when a temporary mast is desired. For example, extendable antennas mounted to television news crews allow the news crew to report and transmit the signal from greater distances. Military posts are often transient in nature, and reducing the time to set up and take down an extendible mast is desirable. There are many other examples of temporary needs for a mast. Keeping the footprint of a mast small is also desirable. It can also be advantageous to provide a mast which can be easily disassembled to facilitate packing and transportation.